Hexahydropyrimidines as fuel additives

ABSTRACT

Distillate fuels containing minor amounts of hexahydropyrimidines sufficient to inhibit fuel deterioration.

This invention relates to improved fuel oil compositions. Moreparticularly, this invention relates to fuel oils which have beenstabilized against the formation of color and sediment therein duringstorage by the addition of a hexahydropyrimidine additive thereto.

In Ser. No. 292,494 filed on September 27, 1972 there is described andclaimed substituted 2, 3, 4, 5-tetrahydropyrimidines (THP) ##SPC1##

which are prepared by the following reactions:

1. The reaction of a carbonyl compound (ketone or aldehyde) with (NH₃ orNH₄ OH) and a sulfur-containing catalyst.

2. The reaction of an α, β -unsaturated ketone and a carbonyl compoundand NH₃ (or NH₄ OH) without a catalyst.

3. Reaction of an α, β -unsaturated ketone, a 1-amino-alcohol and NH₃(or NH₄ OH) without a catalyst.

In the above formula, R₁, R₂, R₃, R₄, R₅ and R₆, which may be the sameor different, are hydrogen or substituted group such as alkyl, aryl,cycloalkyl, alkaryl, aralkyl, heterocyclic, substituted derivativesthereof, etc. In addition R groups may be joined in a cyclicconfiguration which makes the THP structure a part of the substitutedgroup.

Alkyl includes methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl,nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,hexadecyl, heptadecyl, octadecyl, escosyl, docosyl, etc. for examplehaving about 1-25 or more carbons such as from about 1-18 carbons, butpreferably about 1-12 carbons. The term "alkyl" also includes isomers ofthe straight chain where branching occurs.

Cycloalkyl includes cyclopentyl, cyclohexyl, etc. and derivativesthereof such as alkyl cyclohexyl, dialkylcyclohexyl, etc.

Aryl, alkaryl and aralkyl include phenyl, alkylphenyl, polyalkylphenyl,chlorophenyl, alkoxyphenyl, naphthyl, alkylnaphthyl, etc., benzyl,substituted benzyl, etc.

The joining of the R groups into a ring structure include thosestructures derived from reactants of the general formula (CH₂)_(n) C = Osuch as cyclohexanone, cyclopentanone, substituted derivatives thereofsuch as alkyl-cyclohexanone, dialkyl-cyclohexanone.

Ser. No. 406,544 filed Oct. 15, 1973 describes and claims a class ofcompounds which are prepared by reducing THP.

Said Ser. No. 406,544 also describes and claims a unique method ofpreparing HHP which comprises using a formate salt such as ammoniumformate. The use of ammonium formate is unique for the followingreasons:

1. In the preparation of THP from a carbonyl compound and ammonia,ammonium formate operates as a very efficient catalyst without beingconsumed.

2. In the preparation of HHP from THP, ammonium formate serves as areducing agent, yielding CO₂ and NH₃ as byproducts. It is oftenpreferred to form ammonium formate by allowing ammonia to react withformic acid present during the initial phase of the reaction. Thebyproducts, produced in the process of preparing HHP from a carbonylcompound, formic acid and ammonia, are H₂ O, CO₂, and NH₃ and are alleasily removed. The specific reaction is as follows: ##SPC2##

If a symmetric carbonyl compound is employed, i.e., R = CH₂ R' a singleHHP will be produced, for example in the case of cyclohexanone, thereaction may be summarized as follows: ##SPC3##

In the preferred method of Ser. No. 406,544, the carbonyl compound isreacted with ammonia in the presence of ammonium formate (or formic acidso as to form ammonium formate in situ) under pressure to keep thevolatile components in the reaction mixture. The reaction is carried outat a temperature and time sufficient to produce THP, for example at atemperature of 20° - 100°C. or higher, such as from 20°-55°C. forpreferably from 2-18 hrs.

In general the molar ratio of carbonyl to NH₃ to formic acid is at least3 to 3 to 1 but preferably 3 to 3-4 to 1.

After completion of the formation of THP, the reaction mixture isfurther heated, preferably under reduced pressure to remove H₂ O CO₂ andNH₃ at a temperature of 40°-200°C. for 0.5 to 24 hrs. to produce HHP.

The preferred carbonyl compound is cyclohexanone. Not all carbonylcompounds can be used. For example methyl ethyl ketone (MEK) whenreacted with ammonia in the presence of formic acid yields a mixture of2,4,5,6-tetramethyl-2,4-diethyl and2,4-dimethyl-2,4,6-triethyl-2,3,4,5-tetrahydropyrimidine which uponfurther reaction with ammonium formate gives a mixture ofdihydropyridines, a process involving deammoniation rather thanreduction of the tetrahydropyrimidine moiety. However, MEK incombination with cyclohexanone yields the HHP.

Substituted cyclohexanones can also be used. Also mixtures ofcyclohexanones and other ketones or aldehydes can be used so as to yieldmixtures of substituted hexahydropyrimidines.

The following examples are presented by way of illustration and not oflimitation.

EXAMPLE 1 2,2,4,4-Dipentamethylene-5,6-tetramethylenehexahydropyrimidine

A mixture of 294 grams of cyclohexanone and 51 grams of 90 percentformic acid were placed in a pressure reactor. To the mixture was addedwith cooling and stirring 58.6 grams of ammonia gas over a 1/2 hourperiod. The mixture was stirred for 18 hours at ambient temperature. Theresulting product was subjected to a vacuum (25 mm Hg) at 60°C. and thedistillate 18 grams of unreacted cyclohexanone (6 percent) and water wasdiscarded. The product was further heated for 3 hours at 120°-125°C. Theresulting product 237.6 grams (86 percent) was identified as2,2,4,4-Dipentamethylene-5,6-tetramethylene hexahydropyrimidine, b₀.5153°-155°C.

Anal. Calc.ed for C₁₈ H₃₂ N₂ ; C, 78.20; H, 11.67 N, 10.14 Found; C,77.94; H, 11.74 N, 10.08

EXAMPLE 2 2,2,4,4-Dipentamethylene-5,6-tetramethylenehexahydropyrimidine

A mixture of 294 grams of cyclohexanone and 63 grams of ammonium formatewere placed in a pressure reactor. To the mixture was added 41 grams ofammonia gas over a 1 hour period. The mixture was stirred for 18 hoursat ambient temperature. The resulting heterogeneous mixture was heatedunder diminished pressure to 125°C. and kept at 125°C. for 31/2 hours.The resulting product, 238 grams, was identical in all respects to theproduct described in example 1.

In a manner as described in example 1, HHP's were prepared from 2-methylcyclohexanone, 3-methyl cyclohexanone, 4-methyl cyclohexanone, mixtureof cyclohexanone and acetone; cyclohexanone and methyl ethyl ketone;cyclohexanone and cyclopentanone; cyclohexanone and propionaldehyde;cyclohexanone and cycloheptanone.

They are summarized as follows.

                  CARBONYL EMPLOYED                                               ______________________________________                                                                             Molar                                    Ex    A               B              Ratio                                                                         A/B                                      ______________________________________                                        3     2-methyl cyclohexanone                                                                        --                                                      4     3-methyl cyclohexanone                                                                        --                                                      5     4-methyl cyclohexanone                                                                        --                                                      6     cyclohexanone   acetone        2                                        7     cyclohexanone   methyl ethyl ketone                                                                          2                                        8     cyclohexanone   cyclopentanone 1                                        9     cyclohexanone   propionaldehyde                                                                              2                                        10    cyclohexanone   cycloheptanone 1                                        ______________________________________                                    

The products of the above reactions where HHP are prepared aresummarized in the following table: ##SPC4##

    RING Position                                                                              6 5  4   4     2     2                                           Ex. Subst. Group                                                                           R.sub.1                                                                         R.sub.2                                                                          R.sub.3                                                                           R.sub.4                                                                             R.sub.5                                                                             R.sub.6                                     __________________________________________________________________________    1     (CH.sub.2).sub.4                                                                         (CH.sub.2).sub.5                                                                         (CH.sub.2).sub.5                                  2     (CH.sub.2).sub.4                                                                         (CH.sub.2).sub.5                                                                         (CH.sub.2).sub.5                                        --CH (CH.sub.2).sub.3                                                                    --CH (CH.sub.2).sub.4                                                                    --CH (CH.sub.2).sub.4                             3     | | |                                              CH.sub.3   CH.sub.3   CH.sub.3                                                --CH.sub.2 --CH--(CH.sub.2).sub.2                                                        --CH.sub.2 --CH--(CH.sub.2).sub.3                                                        --CH.sub.2 --CH--(CH.sub.2).sub.3 --              4     | | |                                              CH.sub.3   CH.sub.3   CH.sub.3                                                 (CH.sub.2).sub.2 --CH--CH.sub.2 --                                                       (CH.sub.2).sub.2 --CH--(CH.sub.2).sub.2                                                  (CH.sub.2).sub.2 --CH--(CH.sub.2).sub.2 --       5     | | |                                              CH.sub.3   CH.sub.3   CH.sub.3                                              Mixtures                                                                  6   of   CH.sub.3                                                                            H  CH.sub.3                                                                          CH.sub.3                                                                            CH.sub.3                                                                            CH.sub.3                                    Products or  (CH.sub.2).sub.4                                                                  or  (CH.sub.2).sub.5                                                                     or  (CH.sub.2).sub.5                                  Mixtures                                                                           CH.sub.3                                                                            CH.sub.3                                                                         CH.sub.3                                                                          C.sub.2 H.sub.5                                                                     CH.sub.3                                                                            C.sub.2 H.sub.5                             7   of   or C.sub.2 H.sub.5                                                                  H                                                                  Products                                                                           or  (CH.sub.2).sub.4                                                                  or  (CH.sub.2).sub.5                                                                     or  (CH.sub.2).sub.5                                  Mixtures                                                                            (CH.sub.2).sub.4                                                                      (CH.sub.2).sub.5                                                                         (CH.sub.2).sub.5                                 8   of                                                                            Products                                                                           or --(CH.sub.2).sub.3                                                                 or  (CH.sub.2).sub.4                                                                     or  (CH.sub.2).sub.4                                  Mixtures                                                                           --(CH.sub.2).sub.4                                                                     (CH.sub.2).sub.5                                                                         (CH.sub.2).sub.5                                 9   of                                                                        Products or H  C.sub.2 H.sub.5                                                                  or H                                                                              C.sub.3 H.sub.7                                                                     or H   C.sub.3 H.sub.7                                Mixtures                                                                            (CH.sub.2).sub.4                                                                      (CH.sub.2).sub.5                                                                         (CH.sub.2).sub.5                                  10 of                                                                            Products                                                                           or  (CH.sub.2).sub.5                                                                  or  (CH.sub.2).sub.6                                                                     or  (CH.sub.2).sub.6                              __________________________________________________________________________

In addition THP can be prepared by the methods described in said Ser.No. 292,494 and reduced to HHP by any conventional reducing techniquesuch as for example with sodium-ethanol, sodiumborohydride, LiAlH₄,sodium bisulfite, magnesium-methanol, a hydrogenation catalyst such asplatinum, palladium, cobalt, nickel, etc.

EXAMPLE A

To a mixture of 294 grams of cyclohexanone and 5 grams of ammoniumchloride placed in a pressure reactor was added over a 3/4 hour period38.8 grams of ammonia gas. After the addition was completed, the mixturewas stirred for 5 hours at ambient temperature. The product was taken upin toluene and the aqueous phase which separated was discarded. Thetoluene solution was evaporated under diminished pressure to yield 268grams of2,2,4,4-dipentamethylene-5,6-tetramethylene-2,3,4,5-tetrahydropyrimidine.

A sample of 27.4 grams of2,2,4,4-dipentamethylene-5,6-tetramethethylene-2,3,4,5-tetrahydropyrimidinewas dissolved in 50 grams of ethanol. To the ethanolic solution wasadded 6.9 grams of sodium metal at such a rate that a temperature of70°-80°C. was maintained. After the addition was completed, the mixturewas heated for 1 hour at 85°-95°C. The mixture was allowed to cool toambient temperature and water was added. The organic layer whichseparated was taken up in toluene. The toluene solution after washingwith water was evaporated under diminished pressure to yield 22.1 gramsof 2,2,4,4-dipentamethylene-5,6-tetramethylene hexahydropyrimidineidentical to the product prepared in example 1.

EXAMPLE B

To a sample of 27.4 grams of2,2,4,4-dipentamethylene-5,6-tetramethylene-2,3,4,5-tetrahydropyrimidinedissolved in 95 grams of ethanol was added 2 grams of 5 percentplatinum/charcoal catalyst. The mixture was hydrogenated in ahydrogenator for 7 hours at an initial pressure of 40 psi of hydrogen.The catalyst was filtered off and the ethanolic solution evaporatedunder diminished pressure to yield 26 grams of2,2,4,4-dipentamethylene-5,6-tetramethylene hexahydropyrimidineidentical to the product described in example A.

EXAMPLE C

A sample of 81.2 grams of2,2,4,4-dipentamethylene-5,6-tetramethylene-2,3,4,5-tetrahydropyrimidineand 32.3 grams of triethylamine were heated to 85°C. Over a 2 hourperiod was added 23 grams of 90 percent formic acid while a reactiontemperature of 85°C. was maintained. After the addition was completed,the mixture was kept at 85°C. for 16 hours. Water was added and theorganic layer isolated and evaporated under diminished pressure to yield60.3 grams of 2,2,4,4-dipentamethylene-5,6-tetramethylenehexahydropyrimidine.

In summary, the hexahydropyrimidines of this invention contain at leastone cycloalkylene or substituted cycloalkylene and most preferably threecycloalkylene or substituted cycloalkylene groups preferably thosehaving a ring of 5-7 carbons and most preferably 6 carbons, i.e.,cyclohexyl.

These are ideally presented by the following formulae ##SPC5##

where the R's are hydrogen, alkyl, cycloalkyl, alkaryl, aralkyl,heterocyclic, and substituted derivatives thereof and the circlesrepresent cycloalkylene structures.

USE AS FUEL ADDITIVE

As is well known, fuel oils have a tendency to deteriorate in storageand form soluble colored bodies and insoluble sludge therein. Thisdeterioration of the oil is highly undesirable in that it causes seriousadverse effects on the characteristics of the oil, particularly on theignition and burning qualities thereof. It is also a contributoryfactor, along with the presence of other impurities in the oil, such asrust, dirt and moisture, in causing clogging of the equipment parts,such as screens, filters, nozzles, etc., as is explained further herein.An important economical factor is also involved in the problem of oildeterioration in storage, viz., customer resistance. Thus, customersjudge the quality of an oil by its color and they oftentimes refuse topurchase highly colored oils. It will be appreciated then that sincefuel oils of necessity are generally subject to considerable periods ofstorage prior to use, the provision of a practical means for preventingthe deterioration of the fuel oil during storage would be a highlydesirable and important contribution to the art.

The problem of the formation of color bodies and sludge is furtheraggravated because fuels, such as diesel and jet fuels, are oftenpreheated for some time before consumption, thus introducing theadditional problem of thermal instability.

We have now found that oil deterioration, with attendant formation ofcolor and sludge in the oil, can be inhibited by employing thehexahydropyrimidine additives of this invention in the oil. In general,one employs a minor amount of the additive which is sufficient toinhibit oil deterioration with the attendant formation of color andsludge.

The amount of additive employed will vary depending on various factors,for example the particular oil to be stabilized, the conditions ofstorage, etc. The stability of an oil depends largely on the nature ofthe crude oil from which it is made, the type of processing involvedduring refining, etc., and therefore some oils will require moreadditive to stabilize them than others. For example, caustic-treated oilwill, in general, require less additive than untreated oil of similarcharacter. In practice, one generally employs at least about 0.0001percent (1 p.p.m.), such as from about 0.0001 to 0.1 percent (1-1000p.p.m.), for example about 0.0002 to 0.05 percent (2-500 p.p.m.), butpreferably about 0.003 to 0.03 percent (3-300 p.p.m.) based on weight ofoil. Larger amounts, such as 1 percent or higher, can be employed but ingeneral there is usually no commercial advantage in doing so.

Fuel oils in general are contemplated by the invention. The fuel oilswith which this invention is especially concerned are hydrocarbonfractions having an initial boiling point of at least about 100°F. andan end point not higher than about 750°F., and boiling substantiallycontinuously throughout their distillation range. Such fuel oils aregenerally known as distillate fuel oils. It will be understood, however,that this term is not restricted to straight-run distillate fractions.Thus, as is well known to those skilled in the art, the distillate fueloils can be straight-run distillate fuel oils, catalytically orthermally cracked (including hydrocracked) distillate fuel oils, ormixtures of straight-run distillates, naphthas and the like, withcracked distillate stocks. Moreover, such fuel oils can be treated inaccordance with well known commercial methods, such as acid or caustictreatment, solvent refining, clay treatment, etc.

The distillate fuel oils are characterized by their relatively lowviscosities, low pour points, and the like. The principal property whichcharacterizes the contemplated hydrocarbon fractions, however, is thedistillation range. As mentioned herein, this range will lie betweenabout 100°F. and about 750°F. Obviously, the distillation range of eachindividual fuel oil will cover a narrower range falling, nevertheless,within the above-specified limits. Likewise, each fuel oil will boilsubstantially continuously throughout its distillation range.

Especially contemplated herein are Nos. 1, 2 and 3 fuel oils used indomestic heating and as diesel fuel oils, particularly those made upchiefly or entirely of cracked distillate stocks. The domestic heatingoils generally conform to the specifications set forth in A.S.T.M.Specifications D396-48T. Specifications for diesel fuels are defined inA.S.T.M. Specifications D975-48T. Also contemplated herein are fuels forjet combustion engines. Typical jet fuels are defined in MilitarySpecification MIL-F-5624B.

The following diesel fuel test is a standard test for diesel fuelstability and is regarded as a rapid screening test for discovering newsystems, which can be used to stabilize petroleum distillate fuels.

DIESEL FUEL TEST 90 minutes at 300° F.

In the operation of a diesel engine, a portion of the fuel sent to thefuel injection system is injected and burned; the remainder iscirculated back to the fuel reservoir. The injection system is locatedon the engine such that the fuel being returned to the reservoir issubjected to high temperatures. Consequently, diesel fuels shouldexhibit good thermal stability as well as good storage stability. Sincethe fuels used as diesel fuel are interchangeable with furnace oils, thefollowing procedure is used to screen the thermal stability of fuel oilsin general.

The test involves exposing 50 ml. samples of fuel, containing desiredquantities of fuel additives, to the test where a bath is held at 300°F.and the samples are exposed for 90 minutes.

After cooling to room temperature the exposed fuel is passed through amoderately retentive filter paper and the degree of stain on the filterpaper noted. The filter paper pads are compared according to a rating of5, 4, 3, 2 or 1, where 5 = worst and 1 - best.

The data in the following Table shows that excellent stability wasachieved in the 90-minute 300°F. diesel fuel test.

    ______________________________________                                        Test                             20                                           Ex.  Additive    Fuel and Additive Conc.                                                                       (p.p.m.)                                     ______________________________________                                        1    commercial A                                                                              2     2   3   2   1   2   2   3   1   1                      2    commercial B                                                                              3     3   1   2   2   1   1   2   1   2                      3    N,N-di-                                                                       methylcy-                                                                     clohexyl-                                                                     amine       4     4   1   3   3   2   1   3   2   3                      4    Product of                                                                    Example 1   2     1   2   1   2   3   1   2   1   1                      5    Product of                                                                    Example 2   2     1   2   1   2   3   1   2   1   1                      6    Product of                                                                    Example 3   2     1   2   1   2   3   1   2   1   1                      7    Formulation 1                                                                             1     1   1   1   1   2   1   1   1   1                      8    Formulation 2                                                                             1     1   1   1   1   2   1   1   1   1                      9    2,2,4,4-Di-                                                                   pentameth-                                                                    ylene-5,6-te-                                                                 tramethylene-                                                                             4     5   4   4   3   4   3   3   3   4                           2,3,4,5-tetra-                                                                hydropyrimi-                                                                  dine                                                                     ______________________________________                                    

The above tests were carried out with 10 different fuels, each verticalcolumn indicating a different fuel. Each additive was tested at 20p.p.m.

Formulation 1 (Test Example 7) contained product of Example 1 60percent; dispersant 10 percent; metal deactivator 5 percent; solvent 20percent.

Formulation 2 (Test Example 8) contained product of Example 1 60percent; dispersant 15 percent; metal deactivator 5 percent; solvent 20percent.

The dispersant is an acrylic polymer.

The metal deactivator is N,N-disalicylidene-1,3-propanediamine

Note that in contrast the excellent performance of thehexahydropyrimides (Test Examples 4,5,6,7,8) the poor performance of thecorresponding tetrahydropyrimidene (Test Example 9).

Although hexahydropyrimidines are useful as fuel additives per se theirperformance may be enhanced by employing certain auxiliary chemicalaids. Among these chemical aids are dispersants, for example acrylicpolymers of copolymers which can be employed in conjunction with thehexahydropyrimides.

One such auxiliary chemical component is the copolymer derived from anacrylic ester of the formula: ##EQU1## and N-vinyl-2-pyrrolidone, forexample, a copolymer containing the following units: ##EQU2## having amolecular weight for example of at least 50,000, for example50,000-500,000, or higher, but preferably 100,000-400,000 with anoptimum of 300,000-400,000 of which vinyl pyrrolidone comprises at least1 percent by weight, of the polymer, for example 1-30 percent, butpreferably 3-15 percent with an optimum of 5-10 percent; where Y ishydrogen, a lower alkyl group such as methyl, ethyl, etc., Z is anhydrocarbon group having, for example, 1-30 carbon atoms, but preferably8 to 18 carbon atoms. These polymers are preferably acrylic ormethacrylic polymers, or polymers derived from both in conjunction withvinyl pyrrolidone. The Z group on the polymer, which can be the samethroughout or mixed, can be octyl, nonyl, decyl, undecyl, dodecyl,tridecyl, tetradecyl, pentadecyl, octadecyl, etc. Lower alkyl groups canalso be employed such as methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, etc., but they preferably are employed as copolymers of thehigher Z groups, for example a copolymer of dodecyl methacrylate andmethyl acrylate, etc. The acrylic ester units may be derived from one ormore acrylic type monomers and may be fully acrylic or fully methacrylicor both acrylic and methacrylic. The polymer may be random, block,graft, etc.

Also, Z may also be an alkylated aromatic group such as butyl phenyl,amyl phenyl, etc., or a cycloaliphatic group such as cyclohexyl. Thus,non-limiting specific examples of suitable monomeric esters are: methylacrylate, ethyl acrylate, propyl methacrylate, amyl acrylate, laurylacrylate, cetyl acrylate, octadecyl acrylate, amyl methacrylate, laurylmethacrylate, cetyl methacrylate, octadecyl methacrylate, amylphenylmethacrylate, cyclohexyl methacrylate, etc., including the analogousacrylate or methacrylate esters. Copolymers of the above and otheracrylic esters may be used, for example, a copolymer of methyl or ethylacrylate and dodecyl methacrylate in conjunction with vinyl pyrrolidone.However, it should be understood that this description does not precludethe presence of small amounts of unesterified groups being present inthe polymer, i.e., approximately 5 percent or less of where Z=H.

It should be understood, of course, that when the above compounds arepolymerized, the polymerization should not be carried to such an extentas to form polymers which are insoluble or non-dispersible in thepetroleum hydrocarbon used. The polymerization may be carried out bymethods known to the art, such as by heating mildly in the presence of asmall amount of benzoyl peroxide, but the method of polymerization isnot part of this invention. For examples of acrylic-vinyl pyrrolidonecopolymers see French Pat. No. 1,163,033.

                                      VINYL PYRROLIDONE-ACRYLIC ESTER TYPE        RESINS                                                                        __________________________________________________________________________                            Vinyl pyrro-                                                                         Mol                                                                    lidone, per-                                                                         ratio Av. mol                                  Ex.                                                                              Monomer 1                                                                            Monomer 2                                                                            Monomer 3                                                                            cent by wt.                                                                          1:2:3 weight                                   __________________________________________________________________________    1  Tridecyl                                                                             Octadecyl                                                              methacrylate                                                                         methacrylate  7.5    1:1   300,000                                  2  Dodecyl                                                                       methacrylate         10                                                    3  Dodecyl                                                                              Butyl                                                                  methacrylate                                                                         acrylate      15     2:1   400,000                                  4  Octadecyl                                                                     methacrylate         5            450,000                                  5  Tridecyl                                                                      methacrylate         20           350,000                                  6  Octadecyl                                                                            Methyl                                                                 methacrylate                                                                         methacrylate  10     3:1   500,000                                  7  Dodecyl                                                                              Ethyl                                                                  methacrylate                                                                         acrylate      5      4:1   400,000                                  8  Cetyl  Octadecyl                                                                            Butyl                                                           methacrylate                                                                         methacrylate                                                                         methacrylate                                                                         7.5    2.1:0.5                                                                             350,000                                  __________________________________________________________________________

Another auxiliary chemical component is a metal deactivator for examplethose conveniently employed in deactivating copper, iron an other metalsfrom hydrocarbon systems. Typical examples are those described in U.S.Pat. No. 2,282,513. Of course, one skilled in the art is aware that manyother metal deactivators are known and can be employed.

The compounds employed as metal deactivators are preferably of the typeof Schiff bases and may be represented by the formulae

    (1) A - CH = N - R - N = CH - B

and preferably,

    (2) HO - A - CH = N - R - N = CH - B - OH

wherein A and B each represents an organic radical and preferably ahydrocarbon radical. In Formula 2 A and B each preferably represents anaromatic ring or an unsaturated heterocyclic ring in whic the hydroxylradical is attached directly to a ring carbon atom ortho to the - CH =N-group. R represents an aliphatic radical having the two N atomsattached directly to different carbon atoms of the same open chain.

Typical examples of aldehyde and polyamines employed in preparing theseSchiff bases include the following:

ALDEHYDES

Benzaldehyde

2-methylbenzaldehyde

3-methylbenzaldehyde

4-methylbenzaldehyde

2-methoxybenzaldehyde

4-methoxybenzaldehyde

2-naphthaldehyde

1-naphthaldehyde

4-phenylbenzaldehyde

Propionaldehyde

n-Butyraldehyde

Heptaldehyde

Aldol

2-hydroxybenzaldehyde

2-hydroxy-6-methylbenzaldehyde

2-hydroxy-3-methoxybenzaldehyde

2-4-dihydroxybenzaldehyde

2-6-dihydroxybenzaldehyde

2-hydroxynaphthaldehyde-1

1-hydroxynaphthaldehyde-2

Anthrol-2-aldehyde-1

2-hydroxyfluorene-aldehyde-1

4-hydroxydiphenyl-aldehyde-3

3-hydroxyphenanthrene-aldehyde-4

1-3-dihydroxy-2-4-dialdehyde-benzene

2-hydroxy-5-chlorobenzaldehyde

2-hydroxy-3-5-dibromobenzaldehyde

2-hydroxy-3-nitrobenzaldehyde

2-hydroxy-3-cyanobenzaldehyde

2-hydroxy-3-carboxybenzaldehyde

4-hydroxypridine-aldehyde-3

4-hydroxyquinoline-aldehyde-3

7-hydroxyquinoline-aldehyde-8

POLYAMINES

Ethylenediamine

1-2-propylenediamine

1-3-propylenediamine

1-6-hexamethylenediamine

1-10 -decamethylenediamine

1-10-decamethylenediamine

Diethylenetriamine

Triethylenetetramine

Pentaerythrityltetramine

1-2-diaminocyclohexane

Di-(b-aminoethyl)ether

Di-(b-aminoethyl)sulfide

The ratio of hexahydropyrimides to the metal deactivator can vary widelydepending on the particular system, the fuel, etc. employed. Thus, theweight ratio of hexahydropyrimides to metal deactivator may be fromabout 0.1 to 20 or more, such as from about 8-15, but preferably fromabout 10-12.

The weight ratio of hexahydropyrimides to the acrylic type polymer canalso vary widely from about 0.1-20 or more, such as from 8-15, butpreferably from about 10-12.

For ease of handling a concentrate of the additive of this invention ina solvent such as a hydrocarbon, for example in concentrations of 5-75percent or higher, such as from 20-60, but preferably from 40-60percent.

The additives of this invention may also be used in petroleum productsto inhibit the formation of deposits on metal surfaces such as occurs intubes, evaporators, heat exchangers, distillation and cracking equipmentand the like.

We claim:
 1. A distillate fuel containing a minor but deteriorationinhibiting amount of a hexahydropyrimidine having the formula##SPC6##where each of the circles represents a cycloalkylene structurehaving from 5 to 7 carbon atoms and where the R's are hydrogen alkyl,cycloalkyl, alkaryl or aralkyl.
 2. The distillate fuel of claim 1 wherethe hexahydropyrimidine has the formula ##SPC7##where the R's arehydrogen, alkyl, cycloalkyl, alkaryl or aralkyl.
 3. The distillate fuelof claim 1 where the hexahydropyrimidine has the formula ##SPC8##wherethe R's are hydrogen or alkyl.
 4. The distillate fuel of claim 3 wherethe R's in the formula are hydrogen or methyl.
 5. The distillate fuel ofclaim 3 wherein the R's in the formula are hydrogen.
 6. The distillatefuel of claim 3 where the R's in the formula are methyl.